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playwright/docs/class-worker.md
Pavel Feldman e0e836cb6e
doc: split classes into files (#4864)
2021-01-01 15:17:27 -08:00

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id title
class-worker class: Worker

The Worker class represents a WebWorker. worker event is emitted on the page object to signal a worker creation. close event is emitted on the worker object when the worker is gone.

page.on('worker', worker => {
  console.log('Worker created: ' + worker.url());
  worker.on('close', worker => console.log('Worker destroyed: ' + worker.url()));
});

console.log('Current workers:');
for (const worker of page.workers())
  console.log('  ' + worker.url());

worker.on('close')

  • type: <[Worker]>

Emitted when this dedicated WebWorker is terminated.

worker.evaluate(pageFunction[, arg])

  • pageFunction <[function]|[string]> Function to be evaluated in the worker context
  • arg <[EvaluationArgument]> Optional argument to pass to pageFunction
  • returns: <[Promise]<[Serializable]>>

Returns the return value of pageFunction

If the function passed to the worker.evaluate returns a [Promise], then worker.evaluate would wait for the promise to resolve and return its value.

If the function passed to the worker.evaluate returns a non-[Serializable] value, then worker.evaluate returns undefined. DevTools Protocol also supports transferring some additional values that are not serializable by JSON: -0, NaN, Infinity, -Infinity, and bigint literals.

worker.evaluateHandle(pageFunction[, arg])

  • pageFunction <[function]|[string]> Function to be evaluated in the page context
  • arg <[EvaluationArgument]> Optional argument to pass to pageFunction
  • returns: <[Promise]<[JSHandle]>>

Returns the return value of pageFunction as in-page object (JSHandle).

The only difference between worker.evaluate and worker.evaluateHandle is that worker.evaluateHandle returns in-page object (JSHandle).

If the function passed to the worker.evaluateHandle returns a [Promise], then worker.evaluateHandle would wait for the promise to resolve and return its value.

worker.url()